Transcript of "Batteries from cradle to grave"

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In the ClassroomBatteries, from Cradle to GraveMichael J. Smith*Departamento de Química, Universidade do Minho, 4710-057 Braga, Portugal*mjsmith@quimica.uminho.ptFiona M. GraySchool of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, Scotland Employers expect graduates to have an area-specific knowl- perspective of the research, extension, and intended audienceedge and to be able to apply instrumental, interpersonal, were defined, together with a schedule for periodic facilitatorproblem-solving, and systematic skills efficiently. To maximize contact for discussion of progress and monitoring of groupthe number of students achieving high levels of competence, a activity. After a period of group activity, the students submittedgreater emphasis should be placed on activities intended to the results of their research as a short report with supportingdevelop the appropriate skills within the course structure (1). bibliography and also as a poster or oral presentation to an audi-Problem-based learning (PBL) is a widely applied approach ence of colleagues and instructors during a session at the end ofintended to encourage students to learn through the structured the semester. A short text introducing the research assignmentexploration of a research problem. Small teams of students are and a typical student handout has been provided in the support-given an open-ended assignment that they research in order to ing information.present well-supported, evidence-based solutions or strategies in Instructor assessment of student learning in this activity waswritten or oral format. This approach effectively combines positive and the overall impression was that students performedindependent learning with written and oral presentation at a level significantly above their average course grade. Thispractice. improvement was attributed to the high level of motivation, Portable electronic equipment has become an essential underlining the importance of authentic problems for students.component of our everyday lives, and whether the device in Our students showed initiative in fact gathering and in thequestion is a remote-controlled toy, a mobile phone, or a laptop proposal of new solutions to existing problems and investedcomputer, it relies on batteries as a source of power. In 2008, the significant personal effort in self-directed study. The end pro-European Union introduced new legislation to regulate the use ducts delivered as reports, posters, and oral presentations made aof toxic chemicals in batteries and to outline a program for the useful contribution to student skill development, fully vindicat-obligatory recycling of spent batteries. This legislation is expected ing the PBL approach in undergraduate education.to have a widespread impact on both industry and the consumer,and hence, it is timely to look at key issues such as environmental The Chemistry of Batteriesconsequences, public awareness and acceptance, current goodpractice, challenges and practicalities, and the consequences of Electrochemical power sources or batteries are devices thatlegislation that are currently being addressed within Europe, convert energy stored in chemicals into electrical energy. StrictlyNorth America, and Asia. speaking, a battery is made up of an assembly of two or more cells We have identified the area of spent-battery recycling as a connected in a series or parallel configuration (2-7), but overrelevant topic on which to build a PBL activity. Evolving battery the last few decades the terms cell and battery have becomedesign and related disposal issues, relevant to the fields of synonymous. Although credit for the original invention thatelectrochemistry, environmental chemistry, materials chemistry, demonstrated the viability of the concept is generally attributedelectrical engineering and technology, and waste management to Alessandro Volta (1800), various, more practical devices wereand recycling, are reviewed to provide key entry points and useful subsequently developed in a sustained effort to improve theinformation resources for instructors who wish to adopt this efficiency of energy storage and conversion (7). Since the earlyteaching strategy. days of battery science, the development of better portable energy sources has been driven by the needs of manufacturers in theProblem-Based Learning electronics sector. Batteries can be classified as primary (single use) or second- The problem-based learning (PBL) activity based on battery ary (rechargeable), with further subdivision into household (forrecycling was successfully implemented with a class of students in consumer goods such as telephones, flashlights, radios, watches,the third year of chemistry. The students were introduced to the or computers), industrial (for reserve network power, local back-topic through an oral presentation after completing lecture up, or traction), and SLI (for starting, lighting, ignition incourses on environmental chemistry and applied electrochem- vehicles). The principal commercial battery chemistries are listedistry. The class was divided into three-member groups, and in Table 1, together with examples of typical applications.students were assigned problems. Some examples of these Further details of the operational characteristics of these cellsproblems are included in the supporting information. A general may be obtained from refs 2-7. _ _ _162 Journal of Chemical Education Vol. 87 No. 2 February 2010 pubs.acs.org/jchemeduc r 2010 American Chemical Society and Division of Chemical Education, Inc. 10.1021/ed800053u Published on Web 01/12/2010

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In the Classroom Table 1. Chemistry Present in Household, Industrial and SLI Batteries Principal Components Designation Anode/Negative Electrolyte Cathode/Positive Typical Applications PRIMARY Zinc-carbon Zinc sheet NH4Cl or ZnCl2 MnO2, C (mix) Used in a wide range of small portable electronic devices; low-cost modest discharge performance; 1.5 V cell potential Alkaline-manganese Zinc powder KOH MnO2, C (mix) Improved performance version of the ZnC cell, more energy and power but also more expensive; 1.5 V cell potential Mercury Zinc powder NaOH or KOH HgO, C (mix) Previously used in hearing aids, cameras, and calculators, discontinued because of Hg toxicity; 1.35 V cell potential Lithium Lithium foil Organic solvent MnOp, C (mix) Available in range of systems with various and Li salt cathodes with voltages between 1.5 and about 3.6 V; excellent performance; expensive Zinc-air Zinc powder KOH Air, C Principal niche market of hearing aids; good cell performance with nominal 1.4 V, but high self-discharge rate Zinc- Zinc powder KOH Ag2O, C (mix) Typical application in watches or calculators; silver oxide good discharge performance, but expensive because of Ag content; nominal 1.55 V cell potential SECONDARY NiCd Cd KOH NiO(OH) Substantial market presence in portable devices; high cycle life, but suffers from memory effect; nominal 1.2 V cell potential; Cd is toxic NiMH AB5 or AB2 KOH NiO(OH) Substitute for traditional NiCd cell; improved Intermetallic in both electrochemical and environmental compound performance; nominal 1.2 V cell potential Lead-acid Pb H2SO4 PbO2 Generally used in SLI applications, traction battery, or as a reserve power source; high toxicity; nominal 2 V; easy to recycle Lithium ion C, Lix Organic solvent Li(1-x)MnOp High performance cell widely used in and Li salt portable electronic equipment; low environmental impact; nominal 3.6-3.7 V cell potential Li-poly or LiPo C, Lix Polymer gel Li(1-x)MnOp Proposed as substitute for Li ion, probably and Li salt cheaper and safer with comparable performance; nominal 3.7 V All commercial batteries are made up of two electrodes, the nickel-metal hydride (NiMH), and lithium ion (Li ion)anode and the cathode, and an electrolyte. The efficiency of the batteries.battery chemistry depends on the chemical reactions taking placeat the electrodes and the nature of the electrolyte present. In Batteries and Environmental Issuesaddition to these active components, batteries must also containinactive components that have support functions and ensure cell Battery components present no threat to human health oroperation. These inactive components include the casings (often to the environment while the battery is in normal use. However,made of steel) and separators, seals, or labels (typically fabricated when subjected to careless disposal within the household orfrom polymers, paperboard, or paper). The active components workplace, inevitable damage and degradation of the batterythat are currently of greatest environmental concern are those housing changes this situation. The environmental impact ofbased on cadmium, lead, and mercury, and to a lesser degree batteries in landfills (11-14) depends on the battery chemistry,copper, nickel, lithium, silver, and zinc (8). the residual capacity of the battery, the local conditions of Precise up-to-date estimates of the number of household temperature, moisture, and oxygen content, the design andbatteries produced are difficult to obtain (9), but approximate maintenance of the landfill, and the proximity of surface orannual sales in the United States, Europe, and Japan are about groundwater.4, 5.5, and 1.9 billion, respectively (6, 10-13). The secondary Batteries identified for household use are mainly zinc-cell market share is between 10 and 14% of annual sales, and carbon, alkaline-manganese, zinc-air, zinc-silver oxide, andthis is made up of a mixture of nickel-cadmium (NiCd), lithium types. This group of primary batteries continues to make _ _ _r 2010 American Chemical Society and Division of Chemical Education, Inc. pubs.acs.org/jchemeduc Vol. 87 No. 2 February 2010 Journal of Chemical Education 163

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In the Classroomup the majority of batteries consumed, accounting for about 90% batteries that contest the commercial terrain occupied byof the portable battery market (6, 11-14). The commercial lead-acid batteries. However, the highly toxic cadmium anode,success of aqueous electrolyte-based batteries (zinc-carbon, along with the nickel oxide hydroxide cathode and the concen-alkaline-manganese, zinc-air, and zinc-silver oxide) is due trated potassium hydroxide electrolyte, present an environmen-to low material costs, ease of manufacture, and performance tal dilemma.characteristics that are suitable for a wide range of electronic In 1990, NiMH cells with their improved electrochemicaldevices with modest energy and power requirements. Although performance became available commercially and also occupied athese batteries are based on some of the oldest chemistries, they more favorable environmental position. While the electrolytehave been subjected to continuous improvement. It is note- and cathode compositions are similar to those of a NiCd cell, aworthy that the alkaline-manganese, zinc-air, and zinc-silver hydrogen storage anode of nickel-cobalt-rare-earth metal alloyoxide miniature batteries (coin or button format) may contain replaced the toxic cadmium electrode.small quantities of mercury as a corrosion-suppressing additive NiMH technology is generally viewed as being a stopgap, tofor the anode. In Europe, for example, the marketing of button be superseded by lithium-based battery technology. There hasbatteries containing more than 2% of mercury by mass and other been significant electrochemical development in this sector; firstbatteries containing more than 0.0005% of mercury has with the launch of the lithium-ion cell and more recently withbeen prohibited since January 2000. In addition, silver oxide, the lithium polymer (Li-poly) cell. A move to lithium-basedzinc-air, and alkaline button batteries that contain between batteries (both primary and secondary) represents an advance in0.0005% and 2% per cell must also be labeled as not for house- terms of environmental impact. Although the anodic materialshold waste disposal. The mercury-content restrictions have are nontoxic, lithium-ion cells contain flammable electrolytesmotivated structural changes: the introduction of zinc alloy and may also contain moderately toxic composite cathodes.powder anodes, the development of new corrosion suppressors, Li-poly cells contain similar anode and cathode constituentsand modified cathode formulations to maintain prelegislation but incorporate a polymeric gel electrolyte. The advantages ofperformance. this new cell format, such as high electrochemical and safety The lithium nonaqueous primary-battery technology has performance and a thin-cell profile that allows manufacturers toalso progressed significantly since the early 1970s (15, 16). adapt cells to fit available space in new devices, will lead toAlthough substantial market growth has been observed, the cost significant growth of this battery in the market and will requireof lithium-based primary batteries is only justified in specific alterations in disposal strategies.applications where high cell performance is essential. Of all the systems under consideration here, it is the Legislationlead-acid battery predominantly used in SLI, traction, andindustrial energy storage that is the most successfully recycled Although there are differences in the way countries ap-(Figure 1). The greatest contribution to this situation lies in proach health and environmental issues, the content of thefactors such as the inherent value of the scrap metal, the effective regulations applied to industry is similar. In Europe (17-19),spent-battery collecting procedure, the relatively simple structure Asia (19, 20), and North America (21-25), the first stages ofof the battery, and the straightforward nature of the lead- regulation involved limitation of dangerous substance content insmelting process. household batteries. Subsequent legislation regulated the collec- The NiCd secondary battery has been commercially avail- tion and disposal or recycling of industrial and householdable since 1950 and effectively dominated the household sec- batteries. Representation of the battery manufacturing industryondary-battery market until about 1990. It is still produced from the outset has permitted consensual positions to be estab-in the standard battery packaging (cylindrical, button, and flat lished and resulted in the associations of manufacturers andprismatic formats) for household use and in industrial, large-scale importers (26-32) that assume responsibility for coordinationFigure 1. Recycling procedure of lead-acid batteries. (UPS is uninterruptible power supply.) _ _ _164 Journal of Chemical Education Vol. 87 No. 2 February 2010 pubs.acs.org/jchemeduc r 2010 American Chemical Society and Division of Chemical Education, Inc.

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In the Classroomof battery elimination or recycling. Despite legislation to regulate the mass of batteries sold for any given financial year, can bedisposal and recycling, poor public knowledge of the legislation, achieved. In Belgium (27), for example, the collection rate perlack of enforcement, and insufficient budget allocation to person is the highest in the world. To achieve this, it wasregulation (33, 34) have been the major contributors to ineffec- necessary to invest in an intense and continuous public-aware-tive application of these new laws. ness campaign to inform the population about national laws, to motivate participation in collection programs, and to changeThe Disposal Option battery disposal habits. The Belgian program involves schools, public and private services, civic associations, point-of-sale out- Many batteries still end up in landfills or are incinerated lets (supermarkets, jewelers, photographic shops, pharmacies, toybecause of inefficient national collection and recycling schemes. stores), and municipal ecoyards.This is undesirable because of the risk of hazardous chemicals Most collection programs are intended for all types ofcontributing to leachate from landfill (a 25 g NiCd phone household batteries, with sorting taking place at the recyclingbattery can contaminate 750,000 L of groundwater to the installation. As most recycling treatments are sensitive to battery-maximum acceptable concentration limit) or to emissions from type purity, the sorting is a critical phase in the process. Variousincineration plants. For incineration, the quantities of hazardous types of automatic sorting equipment have been developed basedemissions depend on furnace temperature, the volatility of the on magnetic, photographic, UV label detection, and X-raybattery elements, and the efficiency of local treatments applied to fingerprinting. Improvements in sorting rates over the last 10the furnace emissions. Some heavy elements may be concentrated years mean that identification and selection can now be achievedin the furnace slag and require specific and expensive secondary at rates of up to 24 batteries per second with a recognitiontreatment. efficiency of about 99%. This phase of battery treatment no Where disposal is the only end-of-life option, it is possible to longer represents the limiting step of the recycling process.treat heavy metals by stabilization and inertization to avoidleaching. These processes reduce the toxicity by making insolubleor immobilizing the hazardous waste and involve chemical Recycling Procedures for Batteriesreactions between constituents in the waste or with species in a The diversity of battery chemistries has led to a correspond-solid matrix added to the residue. Inertization is generally ingly wide range of recycling treatments. Regardless of theconsidered to be financially nonviable. It requires a battery treatment method undertaken, the preliminary processing stagecollection scheme, and unlike recycling, the inertized materials involves removal of labels, opening of cell casings, and destroyinghave no residual commercial value. seals and separators by procedures based on mechanical cutting,Battery Collection and Sorting Strategies chopping, or pounding, vacuum milling, cryogrinding, or pyro- lysis (Figure 2). The secondary stages of recycling are broadly Although certain segments of the battery market benefit classified as hydrometallurgic or pyrometallurgic.from specific collection routines (for example the lead-acid Hydrometallurgic techniques applied to the cell fragmentsbatteries or large capacity installations of industrial batteries), the include acid, alkaline, or solvent extraction. These proceduresmost challenging market segment is that of household batteries. yield metal solutions that are subsequently subjected to precipi-These batteries are widely dispersed, use a broad variety of tation, selective reactions, electrolysis, or electrodialysis to isolatechemistries, and represent a large portion of the overall cell the purified materials.market. Efficient collection of household batteries depends on Pyrometallurgic procedures, using high temperatures tolegislation and the willingness of the population to recycle spent separate metals, may be subdivided by the final destiny of thecells. Recent studies (32) confirm that high recycling rates, recycled material. One subdivision relates to treatments thatmeasured as a percentage of the mass of recycled batteries to ultimately incorporate the processed battery material as aFigure 2. General recycling procedure for all types of batteries. _ _ _r 2010 American Chemical Society and Division of Chemical Education, Inc. pubs.acs.org/jchemeduc Vol. 87 No. 2 February 2010 Journal of Chemical Education 165

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In the Classroomcomponent in steel production; the other subdivision involves chemical energy from a quick-fill reservoir outside the cell (orspecific processes designed to yield purified elements for reentry stack) structure. As the source of chemical energy is not part ofinto a variety of industrial feedstocks. While the nickel, chro- the cell, the task of recycling these units is greatly simplified. Themium, and manganese residues from recycled batteries are use of precious-metal catalysts in the composite electrode com-acceptable components in steel production, the quantities of ponent of these cells also provides a strong economic motivationcadmium, copper, and zinc must be carefully monitored to avoid for end-of-life collection and recycling treatment. Even beforedeterioration of the steels properties. At the extremely high the routines for end-of-life processing of current primary andfurnace temperatures used in steel production, any residual zinc secondary cells have become well established and before wide-and cadmium (and mercury, should it be present) will evaporate, spread collection strategies have been implemented at a localoxidize, and be emitted from fume stacks as flyash loaded with level, there are clear indications that a new fuel cell-based powerhazardous dust. Although useful, this strategy for battery waste source is gaining commercial viability and that the portabletreatment carries certain limitations. Various companies specia- electronics industry is prepared to welcome this innovation.lize in the production of purified zinc, cadmium, lead, mercury,and nickel using batteries as feedstock. These pure elements are Literature Citedsupplied to other metallurgic companies as raw material, and theslag or bottom-ash containing unwanted residues is separated for 1. Tuning Educational Structures in Europe; The Tuning Manage-use in road or building foundations. ment Committee, University of Deusto: Deusto, Spain, Procedures for recycling lithium battery feedstocks, also 2006. Document available at http://www.tuning.unideusto.org/represented in Figure 2, have been developed by various compa- tuningeu/ (accessed Nov 2009).nies. In the Toxco (hydrometallurgic) treatment (35), lithium is 2. Modern Batteries: An Introduction to Electrochemical Power Sources,recovered as the metal or lithium hydroxide. Initial processing of 2nd ed.; Vincent, C. A., Scrosati, B., Eds.; Arnold: London,battery feedstock involves cryogrinding and reacting with water 1997.to produce hydrogen, which can be burnt off above the reaction 3. Crompton, T. R. Battery Reference Book, 3rd ed.; Elsevier Science:liquid. In pyrometallurgic procedures, component recovery is London, 2000.limited to cobalt and steel-making residues. Other treatments 4. Dell, R. M.; Rand, D. A. J. Understanding Batteries; RSC Publish-(not shown) involve a combined pyro-hydrometallurgical pro- ing: London, 2001.cess where punctured cells are subjected to incineration and 5. Handbook of Batteries, 3rd ed.; Linden, D., Reddy, T. B., Eds.;cobalt is subsequently recovered from metallic waste through the McGraw-Hill: New York, 2002.application of standard hydrometallurgical procedures. With 6. Pistoia, G. Batteries for Portable Devices; Elsevier Science:alternative, less vigorous, purely hydrometallurgical procedures London, 2005.(36), electrolyte and electrode material may also be recovered 7. Heise, G. W.; Cahoon, C. N. Primary Batteries; John Wiley &from the disassembled cells. This latter option is more attractive, Sons, Inc.: New York, 1960; Vol. 1.and even with fluctuations in the market value of recycled 8. The Sigma Aldrich Library of Safety Data, 2nd ed.; Lange, R., Ed.;materials, the fundamental profitability of the process is sup- Sigma-Aldrich Corp.: Milwaukee, WI, 1988.ported by the sale of products rather than from charges levied on 9. Galligan, C.; Morose, G. An Investigation of Alternatives to Minia-battery end-users. ture Batteries Containing Mercury; Lowell Center for Sustainable Production, University of Massachusetts Lowell: Lowell, MA,Future of Battery Technology and Recycling 2004. document available at http://sustainableproduction.org (accessed Nov 2009). Information provided by manufacturers and recycling 10. Directive of the European Parliament and of the Council on Batteriesagencies confirms that treatment of battery residues has arrived and Accumulators and spent Batteries and Accumulators; Commissionat a critical moment when old responsibilities are being addressed Staff Working Paper, Brussels (2003), http://www.epbaeurope.with new strategies. More than ever before, the current consumer net/PositionPapers/RD%20como%20presentation%20final-generation is being made aware of its duty to adopt a socially and %20june%2004%20for%20web.pdfscientifically correct response to preserve the quality of our 11. Broussely, M. Spent Battery Collection and Recycling. In Industrialenvironment. Applications of Batteries: From Cars to Aerospace and Energy Storage; An ever-increasing number of equipment manufacturers are Pistoia, G., Ed.; Elsevier Science: London, 2007; Chapters 14using high-performance lithium-based secondary cells in their and 15.products. Such cells are increasingly of the Li-poly class and pose 12. Hurd, D. J.; Muchnik, D. M.; Schedler, T. M. Recycling of Consumeran interesting conundrum. With foil-bag containers substituting Dry Cell Batteries: Pollution Technology Review, no. 213; Notesthe traditional steel casing, they have minimal recyclable content Data Corp.: Park Ridge, NJ, 1993; pp 210-243.and combine competitive electrochemical performance with 13. Lund, H. F. The McGraw-Hill Recycling Handbook; McGraw-Hillnegligible environmental impact. Future versions of Li-poly Professional: New York, 2001.secondary cells may represent a truly ecological choice of a power 14. Pistoia, G.; Wiaux, J.-P.; Wolsky, S. P. Used Battery Collection andsource in which the toxic chemical content is so low that they can Recycling; Industrial Chemistry Library, Vol. 10; Elseviersafely be disposed of as municipal solid waste. Science: New York, 2001; pp 369-372. Significant advances are also being made in fuel-cell tech- 15. Vincent, C. A. Solid State Ionics 2000, 134, 159–167.nology with several companies involved in the design and 16. Tamura, K.; Horiba, T. J. Power Sources 1999, 81-82, 156–161.manufacture of high-performance fuel cells adapted to the 17. The Battery Directive, Accumulators and Waste Batteriesportable electronics, back-up energy, and traction markets Disposal, Official Journal of the European Union, 26.9.06, Direc-(37-41). These hydrogen or methanol-fuelled cells draw their tive 2006/66/EC, 2006, http://europa.eu/legislation_summaries/ _ _ _166 Journal of Chemical Education Vol. 87 No. 2 February 2010 pubs.acs.org/jchemeduc r 2010 American Chemical Society and Division of Chemical Education, Inc.